1. Field of the Invention
Exemplary embodiments of the present invention relate to an apparatus and a method for detecting a signal in a common frequency band; and, more particularly, to a signal detection apparatus and a method thereof for sensing spectrum in a common frequency band.
2. Description of Related Art
Wireless communication is essentially used in almost all of systems and devices in a ubiquitous society. In such ubiquitous society, frequency shortage has been magnified as the most major problem. As one of solutions to overcome the frequency shortage problem, a common frequency band concept has been introduced to effectively use frequencies. The common frequency band concept allows heterogeneous wireless communication technologies to commonly use a predetermined frequency band.
Recently, Federal Communications Commission (FCC) allows unlicensed use of an unused TV frequency band called “white spaces”. Accordingly, many studies and researches have been actively and globally conducted on a spectrum sharing technology to use the TV frequency band. It is also expected that various dynamic spectrum access technologies would be introduced to share the TV frequency band. Further, a spectrum management technology is also required to control various wireless devices using different communication protocols to share a common frequency band without interference. In order to share the common frequency band, various spectrum sensing technologies have been used.
As a method for determining channel availability, a signal processing algorithm or a channel usage database has been widely used.
As a spectrum sensing technology using a signal processing algorithm, an energy detection based sensing method, a waveform based sensing method, a spectral correlation based sensing method, a radio identification based sensing method, and a matched filter based sensing method have been introduced.
A spectrum sensing technology using a channel usage database can stably detect a signal without a hidden terminal problem. However, the spectrum sensing technology using the channel usage database has drawback. Due to shadow fading or multipath fading, the channel usage database may not be accessed occasionally. Therefore, all devices are required to have capability of detecting a signal through a sensing algorithm.
Recently, many studies have been made to develop a cooperative spectrum sensing technology to overcome the hidden terminal problem. The cooperative spectrum sensing technology allows multiple users to share an individual sensing result with other users. Therefore, each user determines spectrum occupation based on the shared sensing result in the cooperative spectrum sensing technology.
FCC clearly states that all devices must have capability to detect a first user signal through a spectrum sensing algorithm in order to use personal/portable service devices as well as fixed wireless service devices and protect a first user of TV band. That is, FCC suggests detecting an ATSC digital TV signal, a NTSC analog TV signal, and a wireless microphone signal using sensing threshold values of −114 dBm/6 MHz, −114 dBm/100 kHz, and −114 dBm/200 kHz. Here, ATSC stands for Advanced Television Systems Committee and NTSC stands for National Television System Committee.
Meanwhile, an IEEE 802.22 standard group also suggests a wireless regional area network (WRAN) system to detect the ATSC digital TV signal, the NTSC analog TV signal, and the wireless microphone signal using sensing threshold values of −116 dBm/6 MHz, −94 dBm/6 MHz, and −107 dBm/200 kHz.